Silicon wafers are cleaned and inspected, and then they are contained in a shipping box and shipped. The shipping box is a container formed by molding a resin, and used after passing though a box cleaning process to prevent contamination that may occur during packaging and transportation.
A box cleaner is used to clean and dry the shipping box in the box cleaning process, and typically includes a tray, a loader, an unloader, a cleaning bath, an ultrasonic wave generator, a rinsing unit, and a drying system. The tray is a jig used to individually clean components of the shipping box. The loader loads the components of the shipping box onto the tray. The unloader unloads the components of the shipping box after the components of the shipping box are cleaned. The cleaning bath contains a deionized water (DIW) that the components of the shipping box loaded on the tray are dipped and cleaned. The ultrasonic wave generator generates ultrasonic waves at the bottom of the cleaning bath to remove micro-particles. The rinsing unit sprays DIW with high pressure to remove impurities and micro-particles remaining after irradiation of ultrasonic waves. The drying system dries out moisture remaining after a rinsing process using clean dry air (CDA) of high temperature or vacuum.
A conventional box cleaner was configured such that the components of the shipping box are loaded onto the tray and dipped in the cleaning bath with the bottom of the shipping box facing the surface of DIW, that is, with an opening of the shipping box facing downward, for example upside down, to improve a cleaning performance. The box cleaner of this structure has a weakness: when lifting up the tray after cleaning of the components of the shipping box, a large quantity of DIW in the shipping box is lifted up with the tray by surface tension, but not drained. As a result, an excessive load occurs to a lift shaft, and durability of an equipment is reduced.
And, the conventional box cleaner uses a scanning method in a drying process of the shipping box using CDA such that the tray is moved horizontally while a CDA nozzle spraying CDA is fixed. The scanning method is not suitable for a shipping box for wafers of complicated structure having 12 inches or more in diameter. And, an excessive friction occurs to an O-ring of a roller for transferring the tray by weight of the tray, resulting in powder generation. As a result, the shipping box may be contaminated after cleaning of the shipping box.
Meanwhile, after the shipping box is cleaned and dried using the conventional box cleaner, the shipping box should be separated from the tray and pass through a natural drying process in a clean room. Accordingly, the shipping box may be contaminated during the handling process and the natural drying process.